Antibodies specific for the purine and pyrimidine bases of nucleic acids may be obtained using nucleoside- or nucleotide-protein conjugates. Such antibodies react with denatured DNA and with RNA. The objectives of the proposed research are to delineate the utility of these antibodies for immunochemical and biochemical investigations of nucleic acids. Among the studies being pursued are: a) The preparation of antibodies specific for trinucleotide codons and for oligonucleotides as large as hexanucleotides. b) Utilization of nucleoside and oligonucleotide-specific antibodies in a study of the architecture and chemical organization of chromosomes. Immunofluorescent and immunoenzyme techniques are being used to visualize the reaction with chromosomal DNA. c) The investigation of the effects of the nucleic acid-reactive antibodies on living cells. d) The use of the antinucleoside antibodies to analyze nucleic acids for rare bases.